Lack of acclimation of leaf area:sapwood area ratios in piñon pine and juniper in response to precipitation reduction and warming

• Published in: Tree physiology Vol. 39; no. 1; pp. 135 - 142
• Main Authors: McBranch, Natalie A, Grossiord, Charlotte, Adams, Henry, Borrego, Isaac, Collins, Adam D, Dickman, Turin, Ryan, Max, Sevanto, Sanna, McDowell, Nate G
• Format: Journal Article
• Language: English
• Published: Canada Oxford University Press 01.01.2019
• Subjects: stomatal conductance; allometry; water potential; carbon allocation; climate change
• ISSN: 1758-4469; 1758-4469
• DOI: 10.1093/treephys/tpy066

Abstract The leaf area to sapwood area ratios of trees (Al:AS) can shift to maintain homeostatic gas exchange per unit leaf area in response to climate variability. We tested the hypothesis that trees alter their Al:AS ratios in response to long-term warming and reduced precipitation in order to maintain leaf-specific gas exchange rates under more stressful conditions. Whole-tree Al:AS was measured on mature piñon pine (Pinus edulis Engelm.) and one-seed juniper (Juniperus monosperma (Engelm.) Sarg.) trees after 5 years (2012–16) of chronic exposure to increased temperature (+4.8 °C), precipitation reduction (−45%), or both simultaneously. No difference was found in Al:As among treatments for either species. Associated with this lack of shift in Al:As were large changes in pre-dawn leaf water potential and stomatal conductance, consistent with theoretical expectations of interactions between leaf and whole-tree hydraulic supply. Our results suggest that a lack of whole-tree acclimation in Al:As results in the reductions in plant gas exchange and water status associated with long-term warming and reduced precipitation in semi-arid woodlands.